This invention relates in general to telephones, and more particularly to a system for providing power to an Ethernet LAN connected telephone.
Conventional telephones and ISDN phones are normally powered at xe2x88x9248 V DC via tip and ring signal wires. However, telephones which include additional set functionality often require a separate power supply (derived either from an AC source or battery) in order to provide power to some or all telephone features. This results in additional cables or wires to the telephone, which introduces objectionable clutter to a user""s desktop.
In the case of Ethernet LAN connected telephones (often referred to as IP Phones), an international standard is being developed for providing power to such telephones from a central location via an additional xe2x80x9cSparexe2x80x9d pair of wires (the 7/8 pair of wires in a standard RJ-45 jack configuration). This powering arrangement is made possible by the fact that standard Ethernet LAN cables have four pairs of wires, of which only two are used by most common data signaling protocols (e.g. 10BaseT and 100BaseT). However, there is a limit to the amount of power that can be provided in this way. Also, until the international standard has been fully specified and adopted, user concerns will remain unaddressed as to potential problems associated with transporting power through LAN wiring.
According to the present invention, use is made of the second xe2x80x9csparexe2x80x9d pair of wires (the 4/5 pair of wires) in a standard Ethernet cable, in order to deliver power to a telephone set from a local source of AC or battery power. Preferably, the source is located within approximately three meters from the telephone. The powering arrangement of the present invention overcomes the problem of desktop clutter inherent in prior art schemes wherein power is delivered to the telephone via an additional power cord, yet eliminates any concerns associated with delivering power through Ethernet LAN wiring. The system of the present invention may be used to provide AC or battery power to the telephone. Furthermore, use of the second xe2x80x9csparexe2x80x9d wiring pair allows the telephone to be designed for either xe2x80x9cremotexe2x80x9d or xe2x80x9clocalxe2x80x9d spare pair powering (i.e. it allows the set power supply to accommodate the wide range of input voltages required by remote and local power sources).